Oscillation generator



' w. E. Bowen O'SCILLATION GENERATOR March 15, 1932.

Filed Jan. 25. 192-9 INVENTOR.

' TTORNEY I as M stood Patented Mar. 15, 1932 1 UNITED STATES WARD E. BOWEB, OF WASHINGTON, DISTRICT OF COLUMBIA OSCILLATION GENERATOR Application filed January 25, 1929. Serial No. 335,0235. 1

My invention relates to oscillation generators in general, and more particularly to oscillation generators employing frequency controlling means. Q

One of the objects of my invention is to provide a constant frequency oscillation generator employing an electron discharge device amplifier having substantially aperiodic circuits.

Another object of my invention is to provide an arrangement whereby an electro mechanical vibrator and a mechanical vibration generator are caused to cooperate to sustain one another in oscillation.

Still another object of my invention s to provide a constant frequency oscillation generator in which the output of a thermionic electron discharge device is caused to enerize mechanical means having a particular requency characteristic and in which additional means is connected with the mechanical means for transmitting constant frequency oscillations to the input of the thermionic electron discharge device.

A further object of my invention is to provide a constant frequency oscillation generator in which mechanically driven elements sustaining electrical oscillations of a constant frequency are associated with the input of a thermionic electron discharge device and in which a mechanical driving means for the elements is associated with the output circuit of the thermionic electron discharge device.

invention will be more clearly underfrom the following specification and by reference to the accompanying drawing which diagrammatically illustrates my invention.

According to my invention, a tuningfork or other device having definite and predetermined inherent frequency characteristics is maintained .in continuous vibration through the use of very thin piezo electric crystal elements which are mounted on the vibratory portions of the tuning fork or other device to be maintained in vibration by impressing the electric charges from the piezo electric element upon the. input circuit of an amplifier and through an electromagnetic coupling transmitting energy from the output circuit of the amplifier. to the tuning ork or other. device to be maintained in vibration.

Referring to the drawing, a tuning fork 1 of steel or other magnetic material has piezo electric elements 2 and 3 mounted on the vibratory portions thereof. These elements are supported upon the lower portion of the I tines of the fork in positions where the damping of the forks natural period is reduced to a minimum. Cements, such as wax, shellac or sodium or potassium silicate may be used'to support the piezo electric elements metal foil such as tin, aluminum, or bronze fastened to the free surface of the piezo electric element by cements, such as are used to fasten the element to the surfaces of the fork. Coatings electrically deposited upon the free surface of the piezo electric element may be provided by coating the surface of the element with a metal base cement suchas sodium or potassium silicate upon Which finely divided powdered graphite or bronze is lightly scattered and a metal coating electrically deposited. The tuning fork 1 is connected to the input circuit of the amplifier by connection 30. The surfaces of the fork adjacent to the piezoelectric elements function as one of the contacts for the piezo electric elements 2 and 3.

The electron discharge devices comprising the amplifier are coupled into a cascade amplifier arrangement by resistance units 10, 11, 12, 13 14 and 15. Units 10, 12 and 14 are connected with the anode circuits and units 11, 13 and 15 are connected with the grid circuit of the electron discharge devices 6, 7, 8 and 9, respectively. Electrostatic capacities 16, 17 and 18 are connected between I the anode and grid electrodes of the electron discharge devices to transfer energy from the anode circuit of one device to the grid circuit of the succeeding device. Any well known type of cascade amplifier circuit may be employed in place of the circuit illustrated. A source of anode current supply is connected to the anodes of electron discharge devices 6, 7 and 8 through choke coils 19, 20 and 21 and to the anode of electron discharge device 9 through the coils 23 and 24.

Coils 23 and 24 are wound upon cores which are adjusted with respect to the tines 27 and 28 of the tuning fork in order that the force exerted upon the tines by the magnetic field set up by the current flowing through coils 23 and 24 may be of proper magnitude. When the tuning fork is set into vibration by bowing or tapping, a stress is impressed upon the piezo electric elements 2 and 3. The resulting strain upon these elements produces electric charges upon the surfaces of the elements." These charges are impressed upon the input of the amplifier whereupon they are amplified and impressed upon the output circuit of the amplifier. Oscillations from the output circuit are im pressed upon the circuit of electromgnets 24 and 25. The mechanical motion of the tines of the fork is augmented by the force exerted upon them by the magnetic flux set up by the electromagnets and the mechanical vibrations of the tuning fork are sustained.

A greater number of piezo electric elements may be used than shown in the drawing if greater excitation of the input circuit of the amplifier is desired. Arrangements employing only one piezo electric element and an amplifier comprising one electron discharge device are also practical in moderately power oscillation generators. Where a greater number of piezo electric elements are used they may be mounted at various places upon the fork other than shown in the illustration.

While I have described my invention in one of its preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon the invention are intended other than are imposed by the scope of the appended claims.

l/Vhat I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. An oscillating generator comprising in combination, a tuning fork, a plurality of piezo electric elements positioned upon said tuning fork at diametrically opposite points at which the mass of the piezo electric elements have minimum effect upon the frequency of vibration of said fork, electromagnetic means located adjacent said fork, and connections between said piezo electric elements and said electro-magnetic means for sustaining electrical oscillations at substantially constant frequency.

2. An oscillation generator comprising in combination, a tuning fork, a plurality of piezo electric elements, one of said piezo electric elements being disposed on the exterior of one of the tines of said tuning fork, and the other of said piezo electric elements being disposed on the exterior of the other tine of said tuning fork, electro-magnetic means located adjacent said fork, an amplifier system having substantially aperiodic frequency characteristics, said piezo electric elements being connected to the input circuit of said amplifier system, and connections between the output circuit of said amplifier system and said electro-magnetic means for sustaining oscillations of substantially constant fre quency.

3. In a system of the class described the combination of a tuning fork, piezo electric elements individual to each of the tines of said tuning fork and located thereon at places which vibrato mechanically at relatively small amplitude, electro-magnetic means po sitioned adjacent portions of the tuning fork vibrating at maximum amplitude, an amplifying system having a substantially aperiodic frequency characteristic, the input circuit of said amplifying system being connected with said piezo electric elements for transferring electrical impulses of amplified magnitude from said piezo electric elements to said electro-magnetic means whereby the mechanical vibrations of said tuning fork are sustained at substantially constant amplitude.

4. An oscillation generator comprising in combination, a tuning fork, a plurality of piezo electric elements positioned opposite each other upon the tines of said tuning fork, electro-magnetic means located adjacent the upper extremities of each of the tines of said fork, an amplifier system, the input circuit of said amplifier system being connected with said piezo electric elements, the output circuit of said amplifier system being connected with said electro-magnetic means for the generation of electrical oscillations of constant frequency.

5. An oscillation generator comprising in combination, a tuning fork, a plurality of piezo electric elements positioned opposite each other upon the lower portions of the tines of said tuning fork, electro-magnetic means positioned adjacent the extremities of the tines of said tuning fork, an amplifying system, the input circuit of said amplifying system being connected to said piezo electric elements and the output circuit of said amplifying system being connected to said elec tro-magnetic means for generating electrical oscillations of constant frequency.

6. An oscillation generator comprising an aperiodic amplifier circuit including an input system and an output system, a tuning fork having a pair of parallel extending vibratory tines, a connection between said tuning fork and one side of said input system, a pair of piezo electric crystal elements, one of said piezo electric crystal elements having the face thereof engaging the lower portion of one of the tines of said tunin fork, a conductive plate member establishing connection with the opposite face of said last mentioned piezo electric crystal element, the other of said piezo electric crystal elements having one face engaging the other tine of said tuning fork directly opposite the location of said first mentioned piezo electric crystal element, a conductive plate member establishing connection with the opposite face of the last mentioned piezo electric crystal element, said conductive plate members being electrically connected one to the other and connected to the opposite side of said input system, and a pair of electromagnetic driving devices connected in series and in the output system of said aperiodic amplifier and located adjacent the upper extremities of the tines of said tuning fork for driving said tuning fork at constant amplitude whereby oscillations are established through said aperiodic amplifier system at substantially constant frequency.

WARD E. BOWER. 

